Role of manganese on the structure, crystallization and sintering of non-stoichiometric lithium disilicate glasses

Abstract

The structural role of Mn was investigated in a relatively simple non-stoichiometric lithium disilicate (Li₂Si₂O₅) based glass composition. Glasses were prepared by partially replacing SiO₂ by MnO₂ from the base glass belonging to the system Li₂O–K₂O–Al₂O₃–SiO₂. An overall depolymerization of the glass network was observed according to magic angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared (FTIR) spectroscopic studies, suggesting a network modifier role for Mn. However, thermal analysis, phase segregation and nucleation in the glasses suggested that Mn might also act as network former. Moreover, calculated crystal field parameters from UV-Visible spectroscopy, showing high ligand field strength (Δ_o) and Racah inter electronic repulsion (B) indicate the possible existence of Mn as individual molecular entities in the interstitials of the glass network. This paper discusses the implications of this structural role of Mn on the crystallization of bulk glasses and on the sintering behaviour and crystallization of glass powder compacts.